stubborn; willful; unyielding
I was a very headstrong young woman: I knew what I wanted to do, and how I wanted to do it, and no-one could tell me anything.
contentious, headstrong, intractable, obstinate, recalcitrant, refractory
amenable, complaisant, compliant, docile, tractable
Headstrong is a person whose head is strong and hence he doesn't change his opinions, so he is stubborn